Method for mapping a tubular region near the heart

ABSTRACT

A method is provided for mapping electrical activity within a tubular region of or near the heart having a inner circumference, such as a pulmonary vein. The method comprises inserting into the heart a distal end of a mapping catheter. The mapping catheter comprises an elongated tubular catheter body having an outer wall, proximal and distal ends, and at least one lumen extending therethrough. The catheter includes a mapping assembly comprising a tubular structure comprising a pre-formed generally circular main region generally transverse and distal to the catheter body and having an outer circumference. The tubular structure comprises a non-conductive cover over at least the main region of the mapping assembly. A plurality of electrode pairs, each comprising two ring electrodes, are carried by the generally circular main region of the mapping assembly. The method further comprises contacting the outer circumference of the generally circular main region with the inner circumference of the tubular region and mapping the electrical activity within the tubular region with the electrodes along the generally circular main region.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/407,772, filed Apr. 4, 2003, now U.S. Pat. No. 7,181,262, andentitled METHOD FOR MAPPING A TUBULAR REGION NEAR THE HEART, which is adivisional of U.S. patent application Ser. No. 09/943,546, now U.S. Pat.No. 6,711,428, filed Aug. 30, 2001, which is a continuation-in-part ofU.S. patent application Ser. No. 09/551,467, now U.S. Pat. No.6,628,976, filed Apr. 17, 2000, which claims priority to and the benefitof U.S. Provisional Application Ser. No. 60/178,478, filed Jan. 27,2000, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method for mapping a tubular regionof or near the heart, and more particularly, a method for mapping thepulmonary vein.

BACKGROUND OF THE INVENTION

Atrial fibrillation is a common sustained cardiac arrhythmia and a majorcause of stroke. This condition is perpetuated by reentrant waveletspropagating in an abnormal atrial-tissue substrate. Various approacheshave been developed to interrupt wavelets, including surgical orcatheter-mediated atriotomy. Prior to treating the condition, one has tofirst determine the location of the wavelets. Various techniques havebeen proposed for making such a determination. None of the proposedtechniques, however, provide for measurement of the activity within apulmonary vein, coronary sinus or other tubular structure about theinner circumference of the structure.

SUMMARY OF THE INVENTION

A method is provided for mapping electrical activity within a tubularregion of or near the heart having an inner circumference, such as apulmonary vein. The method comprises inserting into the heart a distalend of a mapping catheter. The mapping catheter comprises an elongatedtubular catheter body having an outer wall, proximal and distal ends,and at least one lumen extending therethrough. The catheter includes amapping assembly comprising a tubular structure comprising a pre-formedgenerally circular main region generally transverse and distal to thecatheter body and having an outer circumference. The tubular structurecomprises a non-conductive cover over at least the main region of themapping assembly. A plurality of electrode pairs, each comprising tworing electrodes, are carried by the generally circular main region ofthe mapping assembly. The method further comprises contacting the outercircumference of the generally circular main region with the innercircumference of the tubular region and mapping the electrical activitywithin the tubular region with the electrodes along the generallycircular main region.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a side cross-sectional view of an embodiment of the catheterof the invention.

FIG. 2 is a side cross-sectional view of a catheter body according tothe invention, including the junction between the catheter body andintermediate section.

FIG. 3 is a cross-sectional view of the intermediate section, includingthe junction between the intermediate section and the mapping assembly.

FIG. 4 is a schematic perspective view of the mapping assembly accordingto the invention.

FIG. 5 is a side view of the mapping assembly according to the inventionin a clockwise formation.

FIG. 6 is a side view of the mapping assembly according to the inventionin a counterclockwise formation rotated 90° relative to the assemblydepicted in FIG. 5.

FIG. 7 is a schematic view of the mapping assembly according to theinvention.

FIG. 8 is a schematic view of the mapping assembly according to theinvention depicting the relationship between the first and lastelectrodes.

FIG. 9 is a schematic view of an alternative mapping assembly accordingto the invention.

DETAILED DESCRIPTION

In a particularly preferred embodiment of the invention, there isprovided a catheter having a mapping assembly at its distal end. Asshown in FIG. 1, the catheter comprises an elongated catheter body 12having proximal and distal ends, an intermediate section 14 at thedistal end of the catheter body, a control handle 16 at the proximal endof the catheter body, and a mapping assembly 17 mounted at the distalend of the catheter to the intermediate section.

With reference to FIG. 2, the catheter body 12 comprises an elongatedtubular construction having a single, axial or central lumen 18. Thecatheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A presentlypreferred construction comprises an outer wall 20 made of polyurethaneor PEBAX. The outer wall 20 comprises an imbedded braided mesh ofstainless steel or the like to increase torsional stiffness of thecatheter body 12 so that, when the control handle 16 is rotated, theintermediate section 14 of the catheter 10 will rotate in acorresponding manner.

The outer diameter of the catheter body 12 is not critical, but ispreferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 20 is not critical, but is thinenough so that the central lumen 18 can accommodate a puller wire, leadwires, and any other desired wires, cables or tubes. If desired, theinner surface of the outer wall 20 is lined with a stiffening tube (notshown) to provide improved torsional stability. A particularly preferredcatheter has an outer wall 20 with an outer diameter of from about 0.090inch to about 0.94 inch and an inner diameter of from about 0.061 inchto about 0.065 inch.

The intermediate section 14 comprises a short section of tubing 22having three lumens. The first lumen 30 electrode carries lead wires 50,the second lumen 32 carries a puller wire 64, and the third lumen 34carries a support member 24. The tubing 22 is made of a suitablenon-toxic material that is preferably more flexible than the catheterbody 12. A presently preferred material for the tubing 22 is braidedpolyurethane, i.e., polyurethane with an embedded mesh of braidedstainless steel or the like. The size of each lumen is not critical, butis sufficient to house the lead wires, puller wire or support member.

The useful length of the catheter, i.e., that portion that can beinserted into the body excluding the mapping assembly 17, can vary asdesired. Preferably the useful length ranges from about 110 cm to about120 cm. The length of the intermediate section 14 is a relatively smallportion of the useful length, and preferably ranges from about 3.5 cm toabout 10 cm, more preferably 6 from about 5 cm to about 6.5 cm.

A preferred means for attaching the catheter body 12 to the intermediatesection 14 is illustrated in FIG. 2. The proximal end of theintermediate section 14 comprises an outer circumferential notch 26 thatreceives the inner surface of the outer wall 22 of the catheter body 12.The intermediate section 14 and catheter body 12 are attached by glue orthe like.

If desired, a spacer (not shown) can be located within the catheter bodybetween the distal end of the stiffening tube (if provided) and theproximal end of the intermediate section. The spacer provides atransition in flexibility at the junction of the catheter body andintermediate section, which allows this junction to bend smoothlywithout folding or kinking. A catheter having such a spacer is describedin U.S. Pat. No. 5,964,757, the disclosure of which is incorporatedherein by reference.

At the distal end of the intermediate section 14 is a mapping assembly,as shown in FIGS. 3 to 7. The mapping assembly is formed from the distalend of the support member 24 covered by a non-conductive covering 28.The mapping assembly comprises a generally straight proximal region 38,a generally circular main region and a generally straight distal region40. The proximal region 38 is mounted on the intermediate section 14, asdescribed in more detail below, so that its axis is generally parallelto the axis of the intermediate section. The proximal region 38preferably has an exposed length, e.g., not contained within theintermediate section 14, ranging from about 3 mm to about 12 mm, morepreferably about 3 mm to about 8 mm, still more preferably about 5 mminch, but can vary as desired.

The generally circular main region 39 does not form a flat circle, butis very slightly helical, as shown in FIGS. 4 to 6. The main region 39has an outer diameter preferably ranging to about 10 mm to about 25 mm,more preferably about 12 mm to about 20 mm, still more preferably about15 mm. The transition region 41 of the straight proximal region 38 andgenerally circular main region 39 is slightly curved and formed suchthat, when viewed from the side with the proximal region at the top ofthe circular main region as shown in FIG. 5, the proximal region (alongwith the intermediate section 14) forms an angle α with the curvedregion ranging from about 75° to about 95°, preferably from about 83° toabout 93°, more preferably about 87°. The main region 39 can curve in aclockwise direction, as shown in FIG. 5, or a counterclockwisedirection, as shown in FIG. 6. When the assembly 17 is turned 90°, asshown in FIG. 6, so that the transition region 41 is near the center ofthe main region, the proximal region (along with the intermediatesection 14) forms an angle β with the main region ranging from about 90°to about 135°, preferably from about 100° to about 110°, more preferablyabout 105°.

The support member 24 is made of a material having shape-memory, i.e.,that can be straightened or bent out of its original shape upon exertionof a force and is capable of substantially returning to its originalshape upon removal of the force. A particularly preferred material forthe support member 24 is a nickel/titanium alloy. Such alloys typicallycomprise about 55% nickel and 45% titanium, but may comprise from about54% to about 57% nickel with the balance being titanium. A preferrednickel/titanium alloy is Nitinol, which has excellent shape memory,together with ductility, strength, corrosion resistance, electricalresistivity and temperature stability. The non-conductive covering 28can be made of any suitable material, and is preferably made of abiocompatible plastic such as polyurethane or PEBAX

A series of ring electrodes 36 are mounted on the non-conductivecovering 28 of the generally circular main region 39 of the mappingassembly 17. The ring electrodes 36 can be made of any suitable solidconductive material, such as platinum or gold, preferably a combinationof platinum and iridium, and mounted onto the non-conductive covering 28with glue or the like. Alternatively, the ring electrodes can be formedby coating the non-conductive covering 28 with an electricallyconducting material, like platinum, gold and/or iridium. The coating canbe applied using sputtering, ion beam deposition or an equivalenttechnique.

In a preferred embodiment, each ring electrode 36 is mounted by firstforming a hole in the non-conductive covering 28. An electrode lead wire50 is fed through the hole, and the ring electrode 36 is welded in placeover the lead wire and non-conductive covering 28. The lead wires 50extend between the non-conductive covering 28 and the support member 24.The proximal end of each lead wire 50 is electrically connected to asuitable connector 37, which is connected to a source of RF energy (notshown).

The number of ring electrodes 36 on the assembly can vary as desired.Preferably the number of ring electrodes ranges from about six to abouttwenty, preferably from about eight to about twelve. In a particularlypreferred embodiment, the assembly carries ten ring electrodes. The ringelectrodes 36 are preferably approximately evenly spaced around thegenerally circular main region 39, as best shown in FIG. 7. In aparticularly preferred embodiment, a distance of approximately 5 mm isprovided between the centers of the ring electrodes 36.

FIGS. 7 and 8 show a particularly preferred electrode arrangement. Asexplained above, the generally circular main region 39 is very slightlyhelical, although FIGS. 7 and 8 depict the main region as a flat circle,as it would generally appear when viewed from the distal end of thecatheter. The generally straight distal region 40 forms a tangentrelative to the generally circular main region 39 and contacts the mainregion at a tangent point 43. A first electrode 36 a is provided, whichis the electrode that is on the generally circular main region 39closest to the proximal region 38. A second electrode 36 b is provided,which is the electrode that is on the generally circular main region 39closest to the distal region 40. Preferably, the first electrode 36 a ispositioned along the circumference of the generally circular main region39 at a distance θ of no more than about 55° from the tangent point,more preferably no more than about 48° from the tangent point, stillmore preferably from about 15° to about 36° from the tangent point.Preferably the second electrode 36 b is positioned along thecircumference of the generally circular main region 39 at a distance ωof no more than about 55° from the tangent point, more preferably nomore than about 48° from the tangent point, still more preferably fromabout 15° to about 36° from the tangent point. Preferably the firstelectrode 36 a is positioned along the circumference of the generallycircular main region 39 at a distance γ of no more than 100° from thesecond electrode 36 b, preferably no more than 80° from the secondelectrode, still more preferably from about 30° to about 75° from thesecond electrode.

An alternative electrode arrangement is depicted in FIG. 9. In thisembodiment, the mapping assembly includes a series of ring electrodepairs 35. Each ring electrode pair 35 comprises two closely-spaced ringelectrodes 36. As used herein, the term “ring electrode pair” refers toa pair of ring electrodes that are arranged closer to each other thanthey are to the other adjacent ring electrodes. Preferably the distancebetween two electrodes 36 of an electrode pair 35 is less than about 3mm, more preferably less than about 2 mm, still more preferably fromabout 0.5 mm to about 1.5 mm. The number of electrode pairs 35 can varyas desired, and preferably ranges from 6 to 14 pairs, more preferably 10pairs.

In a particularly preferred embodiment, the mapping assembly carries 10pairs of electrodes with a space of approximately 1 mm between the twoelectrodes 36 of each pair 35. Preferably each ring electrode 36 isrelatively short, having a length ranging from about 0.4 mm to about0.75 mm, with the most distal ring electrode 36 c being longer than theother ring electrodes, preferably having a length ranging from about 1mm to about 1.5 mm. The longer ring electrode provides a signal to theuser when the catheter is being viewed under fluoroscopy. Specifically,because the mapping assembly is generally circular, it can be difficultfor the user to determine which electrodes are placed at a particularlocation in the heart. By having one ring electrode, such as the mostdistal ring electrode, sized differently from the other ring electrodes,the user has a reference point when viewing the catheter underfluoroscopy.

Regardless of the size and number of the ring electrodes 36, theelectrode pairs 35 are preferably approximately evenly spaced around thegenerally circular main region 39. The closely-spaced electrode pairs 35allow for more accurate detection of near field pulmonary vein potentialversus far field atrial signals, which is very important when trying totreat atrial fibrillation. Specifically, the near field pulmonary veinpotentials are very small signals whereas the atria, located very closeto the pulmonary vein, provides much larger signals. Accordingly, evenwhen the mapping array is placed in the pulmonary vein, it can bedifficult for the physician to determine whether the signal is a small,close potential (from the pulmonary vein) or a larger, farther potential(from the atria). Closely-spaced bipoles permit the physician to moreaccurately determine whether he is looking at a close signal or a farsignal. Accordingly, by having closely-spaced electrodes, one is able totarget exactly the locations of myocardial tissue that have pulmonaryvein potentials and therefore allows the clinician to deliver therapy tothe specific tissue. Moreover, the closely-spaced electrodes allow thephysician to determine the exact anatomical location of the ostium bythe electrical signal.

If desired, additional electrodes (not shown) could be mounted along theintermediate section 14, the generally straight proximal section 39, thetransition region 41, and generally straight distal region 40.

The generally straight distal region 40 is provided with an atraumaticdesign to prevent the distal end of the mapping assembly 17 frompenetrating tissue. In the depicted embodiment, the distal region 40comprises a tightly wound coil spring 44 made, for example, of stainlesssteel, such as the mini guidewire commercially available from CordisCorporation (Miami, Fla.) or a coil having a 0.0045 inch wire size and a0.009 inch inner diameter, such as that commercially available fromMicrospring. The coil spring 44 is mounted at its proximal end in ashort piece of tubing 45 with polyurethane glue or the like, which isthen glued or otherwise anchored within the non-conductive covering 28.The tubing 45 is less flexible than the non-conductive covering 28 butmore flexible than that support member 24 to provide a transition inflexibility along the length of the mapping assembly 17. The distal endof the distal region 40 is capped, preferably with polyurethane glue 46,to prevent body fluids from entering the mapping assembly 17. In thedepicted embodiment, the generally straight distal region 40 has alength of about 0.5 inch, but can be any desired length, for example,ranging from about 0.25 inch to about 1.0 inch. The generally straightdistal region 40 is preferably sufficiently long to serve as an anchorfor introducing the catheter into a guiding sheath, as discussed in moredetail below, because the mapping assembly 17 must be straightened uponintroduction into the sheath. Without having the generally straightdistal region 40 as an anchor, the mapping assembly 17 has a tendency topull out of the guiding sheath upon its introduction into the guidingsheath. Any other atraumatic tip design that prevents the distal end ofthe mapping assembly from penetrating tissue could be provided. Analternative design in the form of a plastic ball is described incopending patent application Ser. No. 09/370,605, entitled “ATRIALBRANDING IRON CATHETER AND METHOD FOR TREATING ATRIAL FIBRILLATION”, theentire disclosure of which is incorporated herein by reference.Additionally, if desired, the distal region 40 can be formed, at leastin part, of a radiopaque material to aid in the positioning of themapping assembly 17 under fluoroscopy.

The junction of the intermediate section 14 and mapping assembly 17 isshown in FIG. 3. The non-conductive covering 28 is attached to thetubing 22 of the intermediate section by glue or the like. The supportmember 24 extends from the third lumen 32 into the non-conductivecovering 28. The proximal end of the support member 24 terminates ashort distance within the third lumen 32, approximately about 5 mm, soas not to adversely affect the ability of the intermediate section 14 todeflect. However, if desired, the proximal end of the support member 24can extend into the catheter body 12.

The lead wires 50 attached to the ring electrodes 36 extend through thefirst lumen 30 of the intermediate section 14, through the central lumen18 of the catheter body 12, and the control handle 16, and terminate attheir proximal end in the connector 37. The portion of the lead wires 50extending through the central lumen 18 of the catheter body 12, controlhandle 16 and proximal end of the intermediate section 14 are enclosedwithin a protective sheath 62, which can be made of any suitablematerial, preferably polyimide. The protective sheath 62 is anchored atits distal end to the proximal end of the intermediate section 14 bygluing it in the first lumen 30 with polyurethane glue or the like.

The puller wire 64 is provided for deflection of the intermediatesection 14. The puller wire 64 extends through the catheter body 12, isanchored at its proximal end to the control handle 16, and is anchoredat its distal end to the intermediate section 14. The puller wire 64 ismade of any suitable metal, such as stainless steel or Nitinol, and ispreferably coated with Teflon® or the like. The coating impartslubricity to the puller wire 64. The puller wire 64 preferably has adiameter ranging from about 0.006 to about 0.010 inch.

A compression coil 66 is situated within the catheter body 12 insurrounding relation to the puller wire 64. The compression coil 66extends from the proximal end of the catheter body 12 to the proximalend of the intermediate section 14. The compression coil 66 is made ofany suitable metal, preferably stainless steel. The compression coil 66is tightly wound on itself to provide flexibility, i.e., bending, but toresist compression. The inner diameter of the compression coil 66 ispreferably slightly larger than the diameter of the puller wire 64. TheTeflon® coating on the puller wire 64 allows it to slide freely withinthe compression coil 66. The outer surface of the compression coil 66 iscovered by a flexible, non-conductive sheath 68, e.g., made of polyimidetubing.

The compression coil 66 is anchored at its proximal end to the outerwall 20 of the catheter body 12 by proximal glue joint 70 and at itsdistal end to the intermediate section 14 by distal glue joint 72. Bothglue joints 70 and 72 preferably comprise polyurethane glue or the like.The glue may be applied by means of a syringe or the like through a holemade between the outer surface of the catheter body 12 and the centrallumen 18. Such a hole may be formed, for example, by a needle or thelike that punctures the outer wall 20 of the catheter body 12 which isheated sufficiently to form a permanent hole. The glue is thenintroduced through the hole to the outer surface of the compression coil66 and wicks around the outer circumference to form a glue joint aboutthe entire circumference of the compression coil.

The puller wire 64 extends into the second lumen 32 of the intermediatesection 14. Preferably the puller wire 64 is anchored at its distal endto the distal end of the intermediate section 14, as shown in FIG. 3.Specifically, a T-shaped anchor is formed, which comprises a short pieceof tubular stainless steel 80, e.g., hypodermic stock, which is fittedover the distal end of the puller wire 64 and crimped to fixedly secureit to the puller wire. The distal end of the tubular stainless steel 80is fixedly attached, e.g., by welding, to a cross-piece 82 formed ofstainless steel ribbon or the like. The cross-piece 82 sits beyond thedistal end of the second lumen 32. The cross-piece 82 is larger than thelumen opening and, therefore, cannot be pulled through the opening. Thedistal end of the second lumen 32 is then filled with glue or the like,preferably polyurethane glue. Within the second lumen 32 of theintermediate section 14, the puller wire 64 extends through a plastic,preferably Teflon®, puller wire sheath (not shown), which prevents thepuller wire 64 from cutting into the wall of the intermediate section 14when the intermediate section is deflected.

Longitudinal movement of the puller wire 42 relative to the catheterbody 12, which results in deflection of the intermediate section 14, isaccomplished by suitable manipulation of the control handle 16. Examplesof suitable control handles for use in the present invention aredisclosed, for example, in U.S. Pat. Nos. Re 34,502 and 5,897,529, theentire disclosures of which are incorporated herein by reference.

In use, a suitable guiding sheath is inserted into the patient with itsdistal end positioned at a desired mapping location. An example of asuitable guiding sheath for use in connection with the present inventionis the Preface™ Braiding Guiding Sheath, commercially available fromCordis Webster (Diamond Bar, Calif.). The distal end of the sheath isguided into one of the atria. A catheter in accordance with the presentinvention is fed through the guiding sheath until its distal end extendsout of the distal end of the guiding sheath. As the catheter is fedthrough the guiding sheath, the mapping assembly 17 is straightened tofit through the sheath. Once the distal end of the catheter ispositioned at the desired mapping location, the guiding sheath is pulledproximally, allowing the deflectable intermediate section 14 and mappingassembly 17 to extend outside the sheath, and the mapping assembly 17returns to its original shape due to the shape-memory of the supportmember 24. The mapping assembly 17 is then inserted into a pulmonaryvein or other tubular region (such as the coronary sinus, superior venacava, or inferior vena cava) so that the outer circumference of thegenerally circular main region 39 of the assembly is in contact with acircumference inside the tubular region. Preferably at least about 50%,more preferably at least about 70%, and still more preferably at leastabout 80% of the circumference of the generally circular main region isin contact with a circumference inside the tubular region.

The circular arrangement of the electrodes 36 permits measurement of theelectrical activity at that circumference of the tubular structure sothat ectopic beats between the electrodes can be identified. The size ofthe generally circular main region 39 permits measurement of electricalactivity along a diameter of a pulmonary vein or other tubular structureof or near the heart because the circular main region has a diametergenerally corresponding to that of a pulmonary vein or the coronarysinus. Additionally, because the main region 39 preferably does not forma flat circle, but instead is somewhat helical, as shown in FIG. 4, itis easier for the user to guide the mapping assembly 17 into a tubularregion.

If desired, two or more puller wires can be provided to enhance theability to manipulate the intermediate section. In such an embodiment, asecond puller wire and a surrounding second compression coil extendthrough the catheter body and into an additional off-axis lumen in theintermediate section. The first puller wire is preferably anchoredproximal to the anchor location of the second puller wire. Suitabledesigns of catheters having two or more puller wires, including suitablecontrol handles for such embodiments, are described, for example, inU.S. patent application Ser. No. 08/924,611, filed Sep. 5, 1997; Ser.No. 09/130,359, filed Aug. 7, 1998; Ser. No. 09/143,426, filed Aug. 28,1998; and Ser. No. 09/157,055, filed Sep. 18, 1998, the disclosures ofwhich are incorporated herein by reference.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention.

Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope.

1. A method for mapping electrical activity within a tubular region ofor near the heart having a inner circumference, the method comprising:inserting into the heart a distal end of a mapping catheter comprising:an elongated tubular catheter body having an outer wall, proximal anddistal ends, and at least one lumen extending therethrough, anintermediate section having proximal and distal ends, the proximal endof the intermediate section being attached to the distal end of thecatheter body, and a mapping assembly attached to the distal end of theintermediate section, the mapping assembly comprising: a tubularstructure comprising a pre-formed generally circular main regiongenerally transverse and distal to the catheter body and having an outercircumference, wherein the tubular structure comprises a non-conductivecover over at least the main region of the mapping assembly, and aplurality of electrode pairs, each comprising two ring electrodes,carried by the generally circular main region of the mapping assembly;contacting the outer circumference of the generally circular main regionwith the inner circumference of the tubular region; and mapping theelectrical activity within the tubular region with the electrodes alongthe generally circular main region.
 2. The method according to claim 1,wherein the mapping assembly further comprises a support member havingshape-memory disposed within at least the main region of the mappingassembly.
 3. The method according to claim 1, wherein the mappingassembly further comprises a generally straight distal region distal tothe main region, the generally straight distal region having anatraumatic design to prevent the distal end of the mapping assembly frompenetrating tissue.
 4. The method according to claim 1, wherein themapping assembly further comprises a generally straight proximal regionattached to the catheter body and a transition region connecting theproximal region and the main region.
 5. The method according to claim 1,wherein the generally circular main region has an outer diameter rangingfrom about 10 mm to about 25 mm.
 6. The method according to claim 1,wherein the generally circular main region has an outer diameter rangingfrom about 12 mm to about 20 mm.
 7. The method according to claim 1,wherein the number of ring electrode pairs along the generally circularmain region ranges from about six to about fourteen.
 8. The methodaccording to claim 1, wherein the mapping assembly comprises ten ringelectrode pairs along the generally circular main region.
 9. The methodaccording to claim 1, wherein the ring electrode pairs are approximatelyevenly spaced around the generally circular main region.
 10. The methodaccording to claim 1, wherein the distance between two ring electrodesof each ring electrode pair is less than about 3 mm.
 11. The methodaccording to claim 1, wherein the distance between two ring electrodesof each ring electrode pair is less than about 2 mm.
 12. The methodaccording to claim 1, wherein the distance between two ring electrodesof each ring electrode pair ranges from about 0.5 mm to about 1.5 mm.13. The method according to claim 1, wherein at least some of the ringelectrodes of the electrode pairs have a length ranging from about 0.4mm to about 0.75 mm.
 14. The method according to claim 1, wherein onering electrode has a length longer than the length of the other ringelectrodes.
 15. The method according to claim 1, wherein one ringelectrode has a length ranging from about 1 mm to about 1.5 mm and allof the other ring electrodes each having a length ranging from about 0.4mm to about 0.75 mm.
 16. The method according to claim 1, wherein thetubular region is selected from the group consisting of pulmonary veins,the coronary sinus, the superior vena cava, and the inferior vena cava.17. The method according to claim 1, wherein at least about 50% of theouter circumference of the generally circular main region is in contactwith the inner circumference of the tubular region.
 18. The methodaccording to claim 1, wherein at least about 80% of the outercircumference of the generally circular main region is in contact withthe inner circumference of the tubular region.
 19. A method for mappingelectrical activity within a pulmonary vein of a patient, the methodcomprising: inserting into the pulmonary vein a mapping cathetercomprising: an elongated tubular catheter body having an outer wall,proximal and distal ends, and at least one lumen extending therethrough,an intermediate section having proximal and distal ends, the proximalend of the intermediate section being attached to the distal end of thecatheter body, a mapping assembly attached to the distal end of theintermediate section comprising: a tubular structure comprising apre-formed generally circular main region generally transverse anddistal to the catheter body and having an outer circumference, whereinthe tubular structure comprises a non-conductive cover over at least themain region of the mapping assembly, and a plurality of electrode pairs,each comprising two ring electrodes, carried by the generally circularmain region of the mapping assembly; contacting the outer circumferenceof the generally circular main region with an inner circumference of thepulmonary vein; and mapping the electrical activity within the pulmonaryvein with the electrodes along the generally circular main region. 20.The method according to claim 19, wherein the distance between two ringelectrodes of each ring electrode pair is less than about 2 mm.
 21. Themethod according to claim 19, wherein the distance between two ringelectrodes of each ring electrode pair ranges from about 0.5 mm to about1.5 mm.
 22. The method according to claim 19, wherein at least some ofthe ring electrodes of the electrode pairs have lengths ranging fromabout 0.4 mm to about 0.75 mm.
 23. The method according to claim 19,wherein one ring electrode has a length longer than the length of theother ring electrodes.
 24. The method according to claim 19, wherein onering electrode has a length ranging from about 1 mm to about 1.5 mm andeach of the other ring electrodes has a length ranging from about 0.4 mmto about 0.75 mm.